4,613 research outputs found
Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies
We investigate the use of spiral arm pitch angles as a probe of disk galaxy
mass profiles. We confirm our previous result that spiral arm pitch angles (P)
are well correlated with the rate of shear (S) in disk galaxy rotation curves.
We use this correlation to argue that imaging data alone can provide a powerful
probe of galactic mass distributions out to large look-back times. We then use
a sample of 13 galaxies, with Spitzer 3.6-m imaging data and observed
H rotation curves, to demonstrate how an inferred shear rate coupled
with a bulge-disk decomposition model and a Tully-Fisher-derived velocity
normalization can be used to place constraints on a galaxy's baryon fraction
and dark matter halo profile. Finally we show that there appears to be a trend
(albeit a weak correlation) between spiral arm pitch angle and halo
concentration. We discuss implications for the suggested link between
supermassive black hole (SMBH) mass and dark halo concentration, using pitch
angle as a proxy for SMBH mass.Comment: 14 pages, 6 figures. Accepted for publication in the Astrophysical
Journa
Discovering Black Hole Mass Scaling Relations with Symbolic Regression
Our knowledge of supermassive black holes (SMBHs) and their relation to their
host galaxies is still limited, and there are only around 150 SMBHs that have
their masses directly measured and confirmed. Better black hole mass scaling
relations will help us reveal the physics of black holes, as well as predict
black hole masses that are not yet measured. Here, we apply symbolic
regression, combined with random forest to those directly-measured black hole
masses and host galaxy properties, and find a collection of higher-dimensional
(N-D) black hole mass scaling relations. These N-D black hole mass scaling
relations have scatter smaller than any of the existing black hole mass scaling
relations. One of the best among them involves the parameters of central
stellar velocity dispersion, bulge-to-total ratio, and density at the black
hole's sphere-of-influence with an intrinsic scatter of $\epsilon=0.083\,\
\text{dex}\epsilon \sim 0.3\,\ \text{dex}\sigma$ relation. These relations will inspire black hole physics, test
black hole models implemented in simulations, and estimate unknown black hole
masses on an unprecedented precision.Comment: 9 pages, 3 figures, accepted by NeurIPS 2023 workshop on Machine
Learning and the Physical Science
Discovery of a Planar Black Hole Mass Scaling Relation for Spiral Galaxies
Supermassive black holes (SMBHs) are tiny in comparison to the galaxies they
inhabit, yet they manage to influence and coevolve along with their hosts.
Evidence of this mutual development is observed in the structure and dynamics
of galaxies and their correlations with black hole mass (). For
our study, we focus on relative parameters that are unique to only disk
galaxies. As such, we quantify the structure of spiral galaxies via their
logarithmic spiral-arm pitch angles () and their dynamics through the
maximum rotational velocities of their galactic disks (). In
the past, we have studied black hole mass scaling relations between
and or , separately. Now, we combine the
three parameters into a trivariate --
relationship that yields best-in-class accuracy in prediction of black hole
masses in spiral galaxies. Because most black hole mass scaling relations have
been created from samples of the largest SMBHs within the most massive
galaxies, they lack certainty when extrapolated to low-mass spiral galaxies.
Thus, it is difficult to confidently use existing scaling relations when trying
to identify galaxies that might harbor the elusive class of intermediate-mass
black holes (IMBHs). Therefore, we offer our novel relationship as an ideal
predictor to search for IMBHs and probe the low-mass end of the black hole mass
function by utilizing spiral galaxies. Already with rotational velocities
widely available for a large population of galaxies and pitch angles readily
measurable from uncalibrated images, we expect that the
-- fundamental plane will be a useful tool
for estimating black hole masses, even at high redshifts.Comment: Unedited manuscript (12 pages & 4 figures), accepted for publication
by The Astrophysical Journal Letters on September 15, 202
Spirality: A Novel Way to Measure Spiral Arm Pitch Angle
We present the MATLAB code Spirality, a novel method for measuring spiral arm
pitch angles by fitting galaxy images to spiral templates of known pitch.
Computation time is typically on the order of 2 minutes per galaxy, assuming at
least 8 GB of working memory. We tested the code using 117 synthetic spiral
images with known pitches, varying both the spiral properties and the input
parameters. The code yielded correct results for all synthetic spirals with
galaxy-like properties. We also compared the code's results to two-dimensional
Fast Fourier Transform (2DFFT) measurements for the sample of nearby galaxies
defined by DMS PPak. Spirality's error bars overlapped 2DFFT's error bars for
26 of the 30 galaxies. The two methods' agreement correlates strongly with
galaxy radius in pixels and also with i-band magnitude, but not with redshift,
a result that is consistent with at least some galaxies' spiral structure being
fully formed by z=1.2, beyond which there are few galaxies in our sample. The
Spirality code package also includes GenSpiral, which produces FITS images of
synthetic spirals, and SpiralArmCount, which uses a one-dimensional Fast
Fourier Transform to count the spiral arms of a galaxy after its pitch is
determined. The code package is freely available online; see Comments for URL.Comment: 19 pages, 9 figures, 3 tables. The code package is available at
http://dafix.uark.edu/~doug/SpiralityCode
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